Image forming apparatus

Abstract

The image forming apparatus is capable of changing a state between a first state in which only a first image bearing member and transfer belt contact each other, and a second state in which respective image bearing members are separated from the transfer belt. A second transfer member is located at a first separating portion at which the second transfer member is separated from the image bearing member in the first state, and is located at a second separating position closer to the second image bearing member than the first separating position in the second state to regulate the position of the transfer belt.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 an endless transfer belt that is rotatable; 
 a plurality of image bearing members that bear toner images; and 
 a plurality of transfer members arranged at positions corresponding to the plurality of image bearing members through the transfer belt, wherein the plurality of transfer members transfers the toner images from the corresponding image bearing members to the transfer belt and is movable so as to contact the transfer belt during image formation and is separated from the plurality of image bearing members during non-image formation, 
 wherein one of the plurality of transfer members is a regulating transfer member configured to regulate a position of the transfer belt by moving to a first separating position at which the regulating transfer member is separated from the corresponding image bearing member much more than during the image formation, and a second separating position located at a position closer to the image bearing member than the first separating position, and when the regulating transfer member is located at the second separating position, the corresponding image bearing member and the transfer belt are separated, the transfer belt and the regulating transfer member contact each other, and the other transfer members are separated from the transfer belt. 
 
     
     
       2. An apparatus according to  claim 1 , wherein when the transfer belt is separated from the remaining transfer members, the regulating transfer member is located at the second separating position to increase distances between the remaining transfer members and the transfer belt. 
     
     
       3. An apparatus according to  claim 1 , wherein the regulating transfer member includes a rotatable roller, and when the regulating transfer member is located at the second separating position, is driven in contact with the transfer belt. 
     
     
       4. An apparatus according to  claim 1 , wherein in an all-separating state in which all the image bearing members and the transfer belt are separated, the regulating transfer member is located at the first separating position. 
     
     
       5. An apparatus according to  claim 1 , wherein the image bearing member corresponding to the regulating transfer member is configured to bear a chromatic toner image. 
     
     
       6. An apparatus according to  claim 1 , wherein one of the plurality of image bearing members is configured to bear an achromatic toner image, the apparatus main body is capable of executing a mono-color mode in which only the achromatic toner image is transferred to the transfer belt, and when executing the mono-color mode, the regulating transfer member is located at the first separating position. 
     
     
       7. An apparatus according to  claim 1 , wherein the transfer belt comprises an intermediate transfer belt configured to transfer a toner image from the image bearing members. 
     
     
       8. An apparatus according to  claim 1 , wherein the transfer belt comprises a recording medium conveyance belt configured to convey a recording medium to which a toner image is transferred from the image bearing members. 
     
     
       9. An image forming apparatus comprising:
 an apparatus main body; 
 an endless transfer belt that is rotatable; 
 a first image bearing member that bears a toner image; 
 a plurality of image bearing members including a second image bearing member configured to bear a toner image of a color different from a color of the first image bearing member; 
 a first transfer member configured to be arranged at a position corresponding to the first image bearing member through the transfer belt and transfer a toner image from the first image bearing member to the transfer belt; and 
 a plurality of transfer members configured to be arranged at positions corresponding to the plurality of image bearing members through the transfer belt and transfer toner images from the corresponding image bearing members to the transfer belt, 
 wherein the apparatus main body is capable of changing a state between a first state in which only the first image bearing member and the transfer belt contact each other, and a second state in which the first image bearing member and the respective image bearing members are separated from the transfer belt, and 
 a second transfer member arranged in correspondence with the second image bearing member among the plurality of transfer members is located at a first separating position at which the second transfer member is separated from the second image bearing member in the first state, and is located at a second separating position closer to the second image bearing member than the first separating position in the second state to regulate a position of the transfer belt. 
 
     
     
       10. An apparatus according to  claim 9 , wherein in a case where the second transfer member is positioned at the second separating position, the transfer belt separates from the second image bearing member and contacts the second transfer member. 
     
     
       11. An apparatus according to  claim 9 , wherein the second transfer member includes a rotatable roller, and when the second transfer member is located at the second separating position, is driven in contact with the transfer belt. 
     
     
       12. An apparatus according to  claim 9 , wherein the first image bearing member is located at a most downstream position in a rotational direction of the transfer belt. 
     
     
       13. An apparatus according to  claim 12 , wherein the second image bearing member is adjacent to the first image bearing member in the rotational direction of the transfer belt. 
     
     
       14. An apparatus according to  claim 12 , wherein the first image bearing member bears an achromatic toner image. 
     
     
       15. An apparatus according to  claim 14 , wherein the plurality of image bearing members are configured to bear toner images of different chromatic colors. 
     
     
       16. An apparatus according to  claim 14 , wherein the apparatus main body can switch a state between a third state in which all the first image bearing member and the plurality of image bearing members contact the transfer belt, the second state, and the first state. 
     
     
       17. An apparatus according to  claim 9 , further comprising a driving unit configured to drive the first transfer member and the plurality of transfer members with respect to the transfer belt, the driving unit including a sliding member,
 wherein the sliding member moves in a direction parallel to a rotational direction of the transfer belt to move the first transfer member and the plurality of transfer members. 
 
     
     
       18. An apparatus according to  claim 9 , wherein the transfer belt comprises an intermediate transfer belt configured to transfer a toner image from the image bearing members. 
     
     
       19. An apparatus according to  claim 9 , wherein the transfer belt comprises a recording medium conveyance belt configured to convey a recording medium to which a toner image is transferred from the image bearing members. 
     
     
       20. An apparatus according to  claim 9 , wherein when driving of the transfer belt starts, the apparatus main body is in the second state.